CN108575027B

CN108575027B - System and method for driving light emitting diode and system for preventing current overshoot

Info

Publication number: CN108575027B
Application number: CN201810209264.6A
Authority: CN
Inventors: 保罗·米拉内西; 法比奥·弗拉贾科莫; 毛里齐奥·加尔瓦诺; 罗伯托·彭佐; 恩里科·托纳佐
Original assignee: Infineon Technologies AG
Current assignee: Infineon Technologies AG
Priority date: 2017-03-14
Filing date: 2018-03-14
Publication date: 2020-01-03
Anticipated expiration: 2038-03-14
Also published as: DE102018105742B4; DE102018105742A1; CN108575027A; US20180270923A1; US10420178B2

Abstract

A system and method for driving a light emitting diode and a system for preventing current overshoot are disclosed. In one example, a system includes a load module, a power module, a family module, and a control module. The power module is configured to generate supply power. The loading module is configured to select a subset of Light Emitting Diodes (LEDs) from a set of LEDs. A series of modules is configured to receive the supply power from the power module, dissipate a portion of the supply power, and output a remaining portion of the supply power as load power to a subset of the LEDs. The control module is configured to drive the series of modules to limit an amount of power at a subset of the LEDs.

Description

System and method for driving light emitting diode and system for preventing current overshoot

Technical Field

The present disclosure relates to drivers, such as light emitting diode drivers, configured to control voltage, current, or power provided to a load, such as a string of light emitting diodes.

Background

The driver may control the voltage, current, or power at the load. For example, a Light Emitting Diode (LED) driver may control power provided to a string of LEDs. Some drivers may include a DC-DC converter, such as a buck-boost, buck, boost, or another DC-DC converter. Such a DC-DC converter may be required to vary the power at the load based on the characteristics of the load. For example, when operating the front lighting of a car at a high beam setting, the string of light emitting diodes may require higher power than when operating at a low beam setting.

Disclosure of Invention

In general, the present disclosure relates to techniques for reducing current overshoot and undershoot in a load when changing the number of load cells. For example, in an exemplary automotive application, a Light Emitting Diode (LED) driver may reduce an amount of activated LEDs in a string of LEDs from a first number for a first light beam setting (e.g., high beam) to a second number for a second light beam setting (e.g., low beam). In this example, the LED driver may control a series module (series module) to limit the power output to the LED string after reducing the number of activated LEDs, thereby preventing current overshoot at the LED string.

In one example, a system includes a loading module, a power module, a family module, and a control module. The power module is configured to generate supply power. The loading module is configured to select a subset of LEDs from the set of LEDs. The series of modules is configured to receive supply power from the power module, dissipate a portion of the supply power, and output a remaining portion of the supply power as load power to a subset of the LEDs. The control module is configured to drive the series of modules to limit an amount of power at a subset of the LEDs.

In another example, a method includes generating, by a power module of a circuit, supply power; and selecting, by a loading module of the circuit, a subset of the LEDs from the set of LEDs. The method also includes receiving, by a series of modules of the circuit, supply power from the power module; consuming a portion of the supply power by a series of modules; and outputting, by the series module, a remaining portion of the supply power as load power to the subset of LEDs. The method also includes driving, by a control module of the circuit, a series of modules to limit an amount of power at a subset of the LEDs.

In another example, a system includes a switching logic module, a collection of LEDs, a loading module, a power module, a family module, and a control module. The switching logic module is configured to generate a switching signal. The loading module is configured to selectively bypass each LED in the set of LEDs to form a subset of LEDs based on the switching signal. The power module is configured to output supply power. The series of modules is configured to receive supply power from the power module, dissipate a portion of the supply power, and output a remaining portion of the supply power as load power to a subset of the LEDs. The control module is configured to drive the series of modules to limit an amount of power at a subset of the LEDs.

The details of these and other examples are set forth in the accompanying drawings and the description below. Other features, objects, and advantages will be apparent from the description and drawings, and from the claims.

Drawings

Fig. 1 is a first block diagram illustrating an example system configured to limit an amount of power at a light emitting diode according to one or more techniques of this disclosure.

Fig. 2 is a conceptual diagram illustrating an example circuit of the system of fig. 1 in accordance with one or more techniques of this disclosure.

Fig. 3 is a circuit diagram illustrating an example circuit of the system of fig. 1 in accordance with one or more techniques of this disclosure.

Fig. 4 is a circuit diagram illustrating an exemplary series of modules and control modules of the system of fig. 1 in accordance with one or more techniques of this disclosure.

Fig. 5 is a circuit diagram illustrating an example circuit of the system with analog control of fig. 1 in accordance with one or more techniques of this disclosure.

Fig. 6 is a circuit diagram illustrating an example circuit of the system with digital control of fig. 1 in accordance with one or more techniques of this disclosure.

Fig. 7 is a circuit diagram illustrating an example circuit of the system with overall control of fig. 1 in accordance with one or more techniques of this disclosure.

Fig. 8 is a flow diagram consistent with techniques that may be performed by the example system of fig. 1 in accordance with this disclosure.

Detailed Description

Some systems may use a DC-DC converter to control the amount of power provided to a load, such as a Light Emitting Diode (LED) string. The power output by the DC-DC converter may be controlled based on the number of selected LEDs that are activated. For example, as the number of selected LEDs increases, the power output by the DC-DC converter increases, and as the number of selected LEDs decreases, the DC-DC converter decreases the power output to the selected LEDs. However, when the number of selected LEDs is reduced, the DC-DC converter may provide power at the LED series string that causes the current at the LED series string to overshoot the desired current, which may result in failure of one or more LEDs in the LED string.

Some systems may use a microcontroller or microprocessor configured to prevent the DC-DC converter from providing power that causes the current at the LED string to overshoot the desired current. For example, the microcontroller or microprocessor may inhibit the number of selected LEDs in the LED string from decreasing until the power output by the DC-DC converter stabilizes. However, in some applications, the use of a microcontroller or microprocessor may increase the complexity of the final device. Furthermore, such systems may rely on complex software executing on a microcontroller or microprocessor, which may increase the complexity of the final device. In addition, such systems may rely on interconnections between boards housing microcontrollers or microprocessors, boards housing DC-DC converters, boards housing LEDs, and other boards.

Rather than relying on a microcontroller or microprocessor to limit power at the LEDs, some systems may include series modules (series modules) to limit the power output to the LEDs. For example, the series module may be configured to limit the power output to the LEDs after the number of selected LEDs is reduced to prevent the current at the LEDs from overshooting the desired current. In this way, the series module may prevent the DC-DC converter from providing power at the LED series string that causes the current at the LED series string to overshoot the desired current, without relying on a microcontroller or microprocessor.

Fig. 1 is a first block diagram illustrating an example system 100 configured to limit an amount of power at LEDs 120A-C (collectively LEDs 120) in accordance with one or more techniques of this disclosure. As shown in the example of fig. 1, the system 100 may include a load module 102, a series module 104, a power module 106, a control module 108, a switch logic module 109, and a reference node 118. In some examples, reference node 118 may be ground, a ground plane, or another reference point of system 100.

The LED120 may refer to any semiconductor light source. In some examples, the LED120 may include a p-n junction configured to emit light when activated. In an exemplary application, the LED120 may be included in a headlamp assembly for automotive applications. For example, the LEDs 120 may be a matrix of LEDs to illuminate the road in front of the motor vehicle. In some examples, the LEDs 120 may be associated with one or more beam settings. For example, the loading module 102 may be configured to operate a first combination of LEDs 120 to operate in a low beam setting and a second combination of LEDs 120 to operate in a high beam setting. In some cases, the beam settings of the LEDs 120 may be digitally controlled, for example, by the loading module 102 for adaptive functions. For example, in the automotive example, in response to system 100 detecting an oncoming vehicle, system 100 may change LEDs 120 from operating at a high beam setting to operating at a low beam setting, and in response to system 100 detecting no oncoming vehicle, system 100 may change LEDs 120 from operating at a low beam setting to operating at a high beam setting. Although fig. 1 shows the system 100 including three LEDs 120, the system 100 may include any suitable number of LEDs 120. For example, the system 100 may include fewer LEDs 120 (e.g., only LEDs 120A, only LEDs 120B, only LEDs 120A and 120B) or more LEDs 120 (e.g., four, five, six, or more). Additionally, although fig. 1 shows a load including light emitting diodes 120, in other examples, a different load may be used.

The loading module 102 may include switching elements 122B and 122C (collectively referred to as switching elements 122), and a multi-function switching unit 124. Although fig. 1 shows the loading module 102 to include two switching elements 122, the loading module 102 may include any suitable number of switching elements 122. For example, the loading module 102 may include fewer switching elements 122 (e.g., only switching element 122B, only switching element 122C) or more switching elements 122 (e.g., four, five, six, or more). In some examples, the LEDs 120A may have corresponding switching elements 122A. Although the example load module 102 of fig. 1 shows the load module 102 including the multi-function switch unit 124, in some examples, the multi-function switch unit 124 may be omitted.

The switching element 122 may comprise any device suitable for allowing current to bypass the respective load cell of the LED 120. For example, the switching element 122B may be switched such that the current output from the LED 120A flows through the switching element 122B instead of the LED 120B. Examples of the switching element 122 may include, but are not limited to, a Silicon Controlled Rectifier (SCR), a Field Effect Transistor (FET), and a Bipolar Junction Transistor (BJT). Examples of FETs may include, but are not limited to, Junction Field Effect Transistors (JFETs), Metal Oxide Semiconductor FETs (MOSFETs), double-gate MOSFETs, Insulated Gate Bipolar Transistors (IGBTs), any other type of FET, or any combination thereof. Examples of MOSFETs may include, but are not limited to, PMOS, NMOS, DMOS, or any other type of MOSFET, or any combination thereof. Examples of BJTs may include, but are not limited to, PNP, NPN, heterojunction, or any other type of BJT, or any combination thereof. It should be understood that the switching element 122 may be a high-side switch or a low-side switch. In addition, the switching element 122 may be voltage controlled and/or current controlled. Examples of current-controlled switching elements may include, but are not limited to, gallium nitride (GaN) MOSFETs, BJTs, or other current-controlling elements.

The multi-function switching unit 124 may be configured to drive the switching element 122. For example, the multi-function switching unit 124 may include one or more driver circuits configured to deactivate (e.g., turn off) and activate (e.g., turn on) each of the switching elements 122. In some examples, the multi-function switch unit 124 may drive the switching element 122 according to a signal received from the switching logic module 109. For example, in response to the multi-function switching unit 124 receiving a command to turn on the switching elements 122A and 122B and turn off the switching element 122C, the multi-function switching unit 124 may drive a first signal (e.g., a high voltage) to a control node (e.g., a gate) of the switching elements 122A and 122B to turn on the switching elements 122A and 122B, and may drive a second signal (e.g., a low voltage) to a control node (e.g., a gate) of the switching element 122C to turn off the switching element 122C.

The switching logic module 109 may be configured to determine a target number of LEDs 120 for forming a series string of load cells. The switching logic 109 may receive an indication (e.g., from a user interacting with the system 100) to change the light beam setting of the system 100 from a high beam setting to a low beam setting. In another example, the switch logic module 109 may determine to change the beam setting of the system 100 from a high beam setting to a low beam setting in response to sensor data indicative of an oncoming automobile. In any case, in response to determining the beam setting of system 100, switching logic module 109 can determine the number of load cells corresponding to the beam setting. For example, when the low beam setting is associated with only LEDs 120A, switching logic module 109 may determine that the target number of LEDs 120 used to form the series string of load cells is 1, and when the high beam setting is associated with LEDs 120A-C, switching logic module 109 may determine that the target number of LEDs 120 used to form the series string of load cells is 3. In some examples, the switching logic module 109 may include analog circuitry. In some examples, the switching logic module 109 may be a digital circuit including one or more logic elements and/or timing elements.

The switching logic module 109 may be configured to generate a switching signal that controls the loading module 102 to turn the LED120 on and off. For example, the switching logic module 109 may output a switching signal to the load module 102 that drives the switching element 122B to activate and bypass the LED 120B. In another example, the switching logic module 109 may output a switching signal to the loading module 102 that drives the switching element 122C to activate, thereby bypassing the LED 120C.

The switching logic module 109 may be configured to generate a reference signal indicative of a target power to be output at the LEDs 120 based on a target number of the LEDs 120. For example, the switch logic module 109 may determine an indication of a target number of LEDs 120 that are not bypassed by the load module 102. In this example, the switching logic module 109 may generate a reference signal for output to the control module 108 based on the target number of LEDs 120. For example, switching logic module 109 may increase the reference signal as the number of LEDs 120 not bypassed by load module 102 increases and decrease the reference signal as the number of LEDs 120 not bypassed by load module 102 decreases.

The control module 108 may be configured to drive the series module 104 to limit the maximum power at the LEDs 120. For example, when the power at the LEDs 120 is greater than a threshold, the control module 108 may drive the switching elements of the series module 104 to increase the amount of power dissipated at the series module 104. In this example, when the power at the LEDs 120 is less than a threshold, the control module 108 may drive the switching elements of the series module 104 to reduce the amount of power dissipated at the series module 104.

The control module 108 may be configured to generate an indication of the target power based on the reference signal. For example, the control module 108 may optionally receive a reference signal from the switching logic module 109 indicating an amount of power to be delivered to the LEDs 120. For example, the control module 108 may increase the target power as the reference signal increases and decrease the target power as the reference signal decreases. Additionally or alternatively, the control module 108 may optionally receive a reference signal from the switching logic module 109 indicative of the amount of power to be dissipated by the series module 104.

The power module 106 may be configured to supply power to the series module 104 output. In some examples, the power module 106 may be or include a DC-DC power converter. In some examples, power module 106 may be configured to generate the supply power based on the indication of the target power. For example, the power module 106 may be configured to generate the supply power based on the target power output by the control module 108. Power module 106 may include one or more switch mode power converters including, but not limited to, flyback, buck-boost, buck-boost,

And the like. The power module 106 may include one or more switching elements to turn on and off one or more energy storage components (e.g., an inductor, a capacitor, or another energy storage component).

The series module 104 may be configured to receive a supply voltage and output load power. For example, the series module 104 may be configured to receive a supply voltage from the power module 106 and output load power to a subset of the LEDs 120 that are not bypassed by the load module 102. In some examples, the series module 104 may include a switching element, such as, but not limited to, a MOSFET. In some examples, the series module 104 may include a driver for driving the switching element.

In accordance with one or more techniques, the series module 104 may be configured to limit the amount of power at the LEDs 120. For example, the series module 104 may be configured to receive supply power from the power module 106. In this example, series module 104 may modify the resistance of series module 104 to dissipate a portion of the supply power. In this example, the series module 104 may be configured to output the remaining portion of the supply power as load power to the LEDs 120. In this manner, the family module 104 may prevent the power module 106 from providing the LED120 with an amount of power that causes a damaging current at the LED 120.

Fig. 2 is a conceptual diagram illustrating an example circuit 200 of the system of fig. 1 in accordance with one or more techniques of this disclosure. As shown, the circuit 200 includes a load module 202, a series module 204, a power module 206, a control module 208, a switch logic module 209, and LEDs 220A-G (collectively LEDs 220). Series module 204 may be an example of series module 104 of FIG. 1. The control module 208 may be an example of the control module 108 of FIG. 1. LEDs 220A-G may be examples of LEDs 120 of FIG. 1.

The power module 206 may be configured to receive power from a power source 240. Examples of power supply 240 may include an output of a rectifier, an output of a DC regulator, a battery output, or another voltage that is substantially DC. Power module 206 may be configured to step down (e.g., step down) and/or step up the voltage from power supply 240 to a voltage suitable for output as supply power to the series module 204. In some examples, the power module 206 may modify the supply power based on the target power. For example, in response to receiving the target power from the control module 208, the power module 206 may generate supply power proportional to the target power.

The loading module 202 may be configured to operate the switching elements 222A-C (collectively switching elements 222) to operate the LEDs 220 at different beam settings. For example, the loading module 202 may activate the switch element 222C to activate the LEDs 220C-G as daytime running lights (daylight running light lamps). In another example, the loading module 202 may activate the switching element 222A to activate the LED 220A as a low beam. In another example, the loading module 202 may activate the switch element 222B to activate the LED 220B as a high beam.

The switching logic module 209 may be configured to receive instructions indicative of an operational state (e.g., on, off) of each of the switching elements 222. For example, the switching logic module 209, upon receiving an indication to operate a daytime running light ("DRL"), may output a gate signal to the loading module 202 that activates the switching element 222C to cause the LEDs 220C-G to operate as daytime running lights. In another example, the switch logic module 209, upon receiving an indication to operate the low beam ("LB"), may output a gate signal to the load module 202 that activates the switch element 222A to operate the LED 220A as a low beam. In another example, the switching logic module 209, upon receiving an indication to operate the high beam ("HB"), may output a gate signal to the loading module 202 that activates the switching element 222B to operate the LED 220B as a high beam.

Fig. 3 is a circuit diagram illustrating an example circuit 300 of the system 100 of fig. 1 in accordance with one or more techniques of this disclosure. As shown, the circuit 300 includes a load module 302, a series module 304, a power module 306, a control module 308, a switch logic module 309, and LEDs 320A-B (collectively LEDs 320). The load module 302 may be an example of the load module 102 of FIG. 1. The power module 306 may be an example of the power module 106 of fig. 1. The switch logic 309 may be an example of the switch logic 109 of fig. 1. The LED 320 may be an example of the LED120 of fig. 1.

The series module 304 may be configured to limit the amount of power at the LEDs 320 such that the amount of power at the LEDs 320 is less than a maximum power threshold. For example, gain amplifier 380 may generate an indication of the power at LED 320 based on the voltage at resistor 360. In this example, the error amplifier 382 may generate a gate signal to drive the switching element 384 based on the indication of power at the LED 320 and a maximum power threshold output by the control module 308. More specifically, the error amplifier 382 may generate a gate signal that modifies the resistance of the switching element 384 based on the maximum power threshold and the indication of power at the LED 320 such that the amount of power at the LED 320 is less than the maximum power threshold. For example, the error amplifier 382 may generate a gate signal that causes the switching element 384 to increase the resistance of the series module 304 to prevent the power at the LED 320 from exceeding a maximum power threshold.

The series module 304 may be configured to adjust the amount of power at the LED 320 such that the amount of power at the LED 320 corresponds to the target power. For example, gain amplifier 380 may generate an indication of the power at LED 320 based on the voltage at resistor 360. In this example, the error amplifier 382 may generate a gate signal to drive the switching element 384 based on the indication of power at the LED 320 and the target power output by the control module 308. More specifically, the error amplifier 382 may generate a gate signal that modifies the resistance of the switching element 384 based on the target power and the indication of the power at the LED 320 such that the amount of power output at the LED 320 corresponds to the target power. For example, the error amplifier 382 may generate a gate signal that causes the switching element 384 to increase the resistance of the series module 304 when the power at the LED 320 exceeds a target power, and generate a gate signal that causes the switching element 384 to decrease the resistance of the series module 304 when the power at the LED 320 does not exceed the target power.

The power module 306 may be configured to output supply power based on the voltage at the compensation capacitor 362. For example, the modulator of the power module 306 may generate the duty cycle of the pulse width modulated signal based on a comparison of the voltage at the compensation capacitor 362 and a reference signal to generate the supply power from the voltage output by the power supply 340. Examples of reference signals may include, but are not limited to, triangular signals (e.g., saw-teeth). For example, when the voltage at the compensation capacitor 362 is greater than the instantaneous voltage of the offset triangular signal (e.g., sawtooth), the modulator may output a first signal (e.g., high signal) to cause the power module 306 to stimulate one or more energy storage elements. In some cases, when the voltage at the compensation capacitor 362 is less than or equal to the instantaneous voltage of the offset triangle signal, the modulator may output a second signal (e.g., a low signal) to cause the power module 306 to turn off (e.g., block activation, deactivate, etc.) the one or more energy storage elements.

The control module 308 may be configured to modify the energy level of the compensation capacitor 362 based on an indication of the portion of the supply power dissipated at the series module 304. For example, the control module 308 may decrease the energy level of the compensation capacitor 362 when the indication of the voltage at the series module 304 corresponds to a voltage that exceeds a voltage threshold. When the switching element 384 operates in the active mode, the voltage threshold may be defined to be greater than the drain-source voltage at the switching element 384. More specifically, for example, the gain amplifier 372 may generate an indication of the voltage at the series module 304 based on the voltage at the series module 304. In this example, the error amplifier 374 may modify the energy level of the compensation capacitor 362 based on the voltage threshold and the indication of the voltage at the series module 304. For example, the error amplifier 374 may decrease the energy level of the compensation capacitor 362 (e.g., by decreasing the energy provided to the compensation capacitor 362) when the indication of the voltage at the series module 304 is greater than the voltage threshold, and may increase the energy level of the compensation capacitor 362 (e.g., by increasing the energy provided to the compensation capacitor 362) when the indication of the voltage at the series module 304 is less than the voltage threshold.

The control module 308 may be configured to modify the energy level of the compensation capacitor 362 based on the indication of power at the LED 320. For example, when the indication of power at the LED 320 corresponds to power exceeding a power threshold, the control module 308 may decrease the energy level of the compensation capacitor 362. The power threshold may be a maximum power threshold, a target power, or another power threshold. More specifically, for example, gain amplifier 370 may generate an indication of the power at LED 320 based on the voltage at resistor 360. In this example, the error amplifier 374 may modify the energy level of the compensation capacitor 362 based on the power threshold and the indication of power at the LED 320. For example, the error amplifier 374 may decrease the energy level of the compensation capacitor 362 when the indication of power at the LED 320 is greater than the power threshold, and may increase the energy level of the compensation capacitor 362 when the indication of power at the LED 320 is less than the power threshold.

Fig. 4 is a circuit diagram illustrating an exemplary series of modules 404 and a control module 408 of the system 100 of fig. 1 in accordance with one or more techniques of this disclosure. Although not shown, it should be understood that the circuit 400 may include other modules (e.g., a load module, a power module, and a switching logic module as described in fig. 1).

The control module 408 may be configured to include a driver for the series module 404. For example, control module 408 may include a gain amplifier 470 substantially similar to gain amplifier 370 of fig. 3, a gain amplifier 472 substantially similar to gain amplifier 372 of fig. 3, and an error amplifier 474 substantially similar to error amplifier 374 of fig. 3. However, the control module 408 may also include a logic module 489 and an error amplifier 482. Logic module 489 may be configured to generate a first power threshold and a second power threshold based on the received reference signal indicative of the target power. The logic block 489 may include analog circuitry. In some examples, logic module 489 may be a digital circuit including one or more logic elements and/or timing elements.

The control module 408 may generate a control signal for driving the switching element 484 of the series module 404 based on the indication of power at the LEDs 420A-420B (collectively referred to as LEDs 420) output by the gain amplifier 470 and a power threshold. For example, gain amplifier 470 may generate an indication of the power at LED 420 based on the voltage at resistor 460. In this example, the error amplifier 482 may generate the control signal based on the indication of power at the LED 420 and a power threshold. In this example, the series module 404 may be configured to modify a resistance of the series module 404 based on the control signal. In this manner, the components of the series module 404 may be integrated into the control module 408 to reduce the number of components in the final device.

Fig. 5 is a circuit diagram illustrating an example circuit 500 of the system 100 of fig. 1 with analog control in accordance with one or more techniques of this disclosure. As shown, the circuit 500 may include a series module 504, a power module 506, a control module 508, a logic module 589, and an LED 520. Series module 504 may be an example of series module 104 of fig. 1. Logic module 589 may be an example of logic module 489 of fig. 4. LED520 may be an example of LED120 of fig. 1. Although not shown, it should be understood that the circuit 500 may include other modules (e.g., the load module depicted in fig. 1).

The control module 508 may be configured to include a driver for the series module 504. For example, control module 508 may include a gain amplifier 570 substantially similar to gain amplifier 470 of fig. 4, a gain amplifier 572 substantially similar to gain amplifier 472 of fig. 4, an error amplifier 574 substantially similar to error amplifier 474 of fig. 4, and an error amplifier 582 substantially similar to error amplifier 482 of fig. 4. However, the logic module 589 may also be configured to a use mode, and the control module 508 may also include the voltage control logic 586. In some examples, the control module 508 may be an analog circuit. For example, logic module 589, gain amplifier 570, gain amplifier 572, error amplifier 474, error amplifier 482, and voltage control logic 586 may each include analog components and omit digital components. Examples of analog components may include, but are not limited to, operational amplifiers, switching elements, diodes, and other analog components. Examples of digital components may include, but are not limited to, logic gates, microprocessors, microcontrollers, and other digital components.

The logic module 589 may be configured to generate a power threshold based on the mode and the indication of the reference power. For example, the logic module 589 may receive an indication of a selection of a mode ("mode" of fig. 5) and an indication of a reference power ("set" of fig. 5). Examples of modes may include, but are not limited to: limiting the amount of power at the LED520 such that the amount of power at the LED520 is less than a maximum power threshold, adjusting the amount of power at the LED520 such that the amount of power at the LED 320 corresponds to a target power, and other modes. In some examples, the logic module 589 may be an analog circuit. For example, the logic module 589 may include analog components and omit digital components.

The logic module 589 may be configured to operate in a mode that limits the amount of power at the LED520 such that the amount of power at the LED520 is less than a maximum power threshold. For example, the logic module 589 may receive an indication of a maximum reference power at a "set" input and an indication of an instruction to limit the amount of power at the LED520 such that the amount of power at the LED520 is less than the maximum reference power at a "mode" input. For example, a logic high value ("1") at the "mode" input may indicate an instruction to limit the amount of power at the LED520 such that the amount of power at the LED520 is less than the maximum reference power. In some cases, the voltage at the "set" input may correspond to a setting of a maximum power threshold. In this example, the logic module 589 may output a power threshold to the error amplifier 582 that is less than the maximum reference power. For example, the power threshold may be between 70% and 95% of the maximum reference power. In this example, the error amplifier 582 may generate a gate signal to drive the switching element 584 based on the indication of power at the LED520 output by the gain amplifier 570 and the power threshold output by the logic block 589. More specifically, the error amplifier 582 may cause the switching element 584 to modify the resistance of the switching element 584 based on a power threshold and the indication of power such that the amount of power at the LED520 is less than the indication of the maximum reference power. For example, the error amplifier 582 may generate a gate signal that causes the switching element 584 to increase the resistance of the series module 504 to prevent the power at the LED520 from exceeding the maximum reference power.

The logic module 589 may be configured to operate in a mode that adjusts the amount of power at the LED520 such that the amount of power at the LED520 corresponds to the target power. For example, the logic module 589 may receive an indication of the target reference power at a "set" input and an indication of an instruction to adjust the amount of power at the LED520 such that the amount of power at the LED520 corresponds to the target reference power at a "mode" input. For example, a logic high value ("0") at the "mode" input may indicate an instruction to limit the amount of power at the LED520 such that the amount of power at the LED520 corresponds to the target reference power. In some cases, the voltage at the "set" input may correspond to a setting of the target power. In this example, the logic module 589 may output a target power to the error amplifier 582 that is approximately equal to or greater than the target reference power. For example, the target power may be between 95% and 125% of the target reference power. In this example, the error amplifier 582 may generate a gate signal to drive the switching element 584 based on the indication of power at the LED520 output by the gain amplifier 570 and the target threshold power output by the logic module 589. More specifically, the error amplifier 582 may cause the switching element 584 to modify the resistance of the switching element 584 based on the target power and the indication of the power such that the amount of power at the LED520 corresponds to the target reference power. For example, the error amplifier 582 may generate a gate signal that causes the switching element 584 to increase the resistance of the series module 504 to control the amount of power at the LED520 to correspond to the target reference power.

Voltage control logic 586 may be configured to selectively drive switching elements 590-593 based on the voltage at compensation capacitor 562. For example, the modulator of voltage control logic 586 may generate a duty cycle of the pulse width modulated signal for generating the supply power based on a comparison of the voltage at compensation capacitor 562 and a reference signal. For example, when the voltage at the compensation capacitor 562 is greater than the instantaneous voltage of an offset triangular signal (e.g., sawtooth), the modulator of the voltage control logic 586 may output a first signal (e.g., a high signal) to cause the switching elements 590-593 to excite the inductor 594. In some cases, when the voltage at compensation capacitor 562 is less than or equal to the instantaneous voltage of the offset triangle signal, the modulator of voltage control logic 586 may output a second signal (e.g., a low signal) to cause switching elements 590-593 to turn off inductor 594 (e.g., de-energize, block energizing, etc.).

Voltage control logic 586 may be configured to actively discharge inductor 594. For example, in response to determining that the next target power is less than the previous target power, voltage control logic 586 may deactivate the control loop and instead effectively discharge the voltage through inductor 594 to ground, thereby changing the voltage at the output of voltage converter 506 from the first supply power to the second supply power.

Fig. 6 is a circuit diagram illustrating an example circuit 600 of the system 100 of fig. 1 with digital control in accordance with one or more techniques of this disclosure. As shown, the circuit 600 may include a series module 604, a power module 606, a control module 608, a logic module 689, and an LED 620. Series module 604 may be an example of series module 104 of fig. 1. Power module 606 may be substantially similar to power module 506 of fig. 5. Logic module 689 may be an example of logic module 489 of fig. 1. LED620 may be an example of LED120 of fig. 1. Although not shown, it should be understood that the circuit 500 may include other modules (e.g., the load module depicted in fig. 1).

The control module 608 may be configured to include a driver for the series module 604. For example, control module 608 may include a gain amplifier 670 substantially similar to gain amplifier 570 of fig. 5, a gain amplifier 672 substantially similar to gain amplifier 572 of fig. 5, and an error amplifier 682 substantially similar to error amplifier 582 of fig. 5. However, the control module 608 may also include a proportional-integral-derivative controller 674. In some examples, the control module 508 may include digital circuitry. For example, the proportional-integral-derivative controllers 674 may each include digital components.

The proportional-integral-derivative controller 674 may be configured to generate an indication of the target power based on the power at the series module 604. For example, the gain amplifier 672 may generate an indication of the power at the series module 604 based on the voltage at the series module 604. In this example, the proportional-integral-derivative controller 674 may decrease the target power when the voltage at the series module 604 exceeds a voltage drop threshold ("droop").

Logic block 689 may be substantially similar to logic block 589 of fig. 5. For example, the logic module 689 may be configured to operate in a mode that limits the amount of power at the LEDs 620 such that the amount of power at the LEDs 620 is less than a maximum power threshold. In another example, the logic module 689 may be configured to operate in a mode that adjusts the amount of power at the LED620 such that the amount of power at the LED620 corresponds to the target power.

The proportional-integral-derivative controller 674 may be configured to generate an indication of the target power based on the power threshold. For example, the proportional-integral-derivative controller 674 may receive the power threshold from the logic module 689. In this example, gain amplifier 670 may generate an indication of power at LED620 based on the voltage at resistor 660. In this example, the proportional-integral-derivative controller 674 may modify the target power output to the voltage control logic 686 based on a power threshold and an indication of power at the LED 620. For example, proportional-integral-derivative controller 674 may decrease the target power output when the power threshold is greater than the indication of power at LED620, and may increase the target power output when the power threshold is less than the indication of power at LED 620.

The proportional-integral-derivative controller 674 may be configured to generate an indication of the target power based on the power at the series module 604, the power threshold, and the indication of power at the LED 620. For example, the gain amplifier 672 may generate an indication of the power at the series module 604 based on the voltage at the series module 604. In this example, gain amplifier 670 may generate an indication of power at LED620 based on the voltage at resistor 660. In this example, the proportional-integral-derivative controller 674 may decrease the target power when the indication of the voltage at the series module 604 exceeds a power threshold ("droop"). In this example, the proportional-integral-derivative controller 674 may increase the target power when the indication of power at the series module 604 does not exceed the power threshold ("droop"), and when the power threshold is less than the indication of power at the LED 620.

Fig. 7 is a circuit diagram illustrating an example circuit 700 of the system 100 of fig. 1 with overall control in accordance with one or more techniques of this disclosure. As shown, the circuit 700 may include a loading module 702, a series module 704, a power module 706, a control module 708, a logic module 789, and an LED 720. Series module 704 may be an example of series module 104 of fig. 1. Power module 706 may be substantially similar to power module 506 of fig. 5 and/or power module 606 of fig. 6. Logic module 789 may be an example of logic module 489 of fig. 1. LED 720 may be an example of LED120 of fig. 1.

The loading module 702 may be configured to select the subset of LEDs 720 based on the switching signal received from the logic module 789. For example, the loading module 702 may select the number of LEDs 720 that are activated (e.g., turned on) based on one or more signals received from the logic module 789. For example, when the one or more signals received from the logic module 789 indicate a fewer number of LEDs 720 than the currently active LEDs, the loading module 702 activates one or more switching elements to bypass one or more LEDs 720.

The series module 704 may be configured to decouple the power module 706 from the LED 720 when the loading module 702 selects the LED 720. For example, when the loading module 702 selects the LED 720, the logic module 789 may set the power threshold to a minimum power threshold. The minimum power threshold may be, but is not limited to, about 0% to 5% of the nominal operating power. In this example, the error amplifier 782 may increase the resistance of the switching element 784 based on the power threshold and the indication of power at the LED 720 output by the gain amplifier 770, such that the resistance of the switching element 784 electrically decouples the power module 706 from the LED 720.

Fig. 8 is a flow diagram consistent with techniques that may be performed by the example system of fig. 1 in accordance with this disclosure. For purposes of illustration only, fig. 8 is described below in the context of the system 100 of fig. 1, the circuit 200 of fig. 2, the circuit 300 of fig. 3, the circuit 400 of fig. 4, the circuit 500 of fig. 5, the circuit 600 of fig. 6, and the circuit 700 of fig. 7. However, the techniques described below may be used in any permutation and any combination of the load module 102, series module 104, power module 106, control module 108, and switch logic module 109.

In accordance with one or more techniques of this disclosure, the control module 108 generates an indication of power at the LED120 (802). For example, the gain amplifier 370 of fig. 3 generates an indication of the power at the LED 320 as a function of the voltage at the resistor 360. The control module 108 generates an indication of power at the series module 104 (804). For example, the gain amplifier 372 of fig. 3 generates an indication of the power at the series module 304.

The control module 108 generates an indication of the target power based on the indication of power at the LEDs 120 and the indication of power at the series module 104 (806). For example, error amplifier 374 of fig. 3 generates the target power based on the indication of power at LED 320 output by gain amplifier 370 and the indication of power at series module 304 output by gain amplifier 372. More specifically, the error amplifier 374 of fig. 3 may charge the compensation capacitor 362 when the indication of power at the series module 304 does not exceed the voltage threshold and the power at the LED120 does not exceed the power indicated by the reference signal. In another example, the proportional-integral-derivative amplifier 674 of fig. 6 generates the target power based on the indication of power at the LED620 output by the gain amplifier 670 and the indication of power at the series module 604 output by the gain amplifier 672.

The power module 106 generates supply power based on the target power (808). For example, the modulator of the power module 306 of fig. 3 selects the duty cycle based on the voltage at the compensation capacitor 362 of fig. 3. In this example, the power module 306 generates the supply power based on a duty cycle. In another example, voltage control logic 686 of fig. 6 controls power module 606 of fig. 6 to generate supply power based on the target power.

The control module 108 determines the power threshold of the LED120 (810). For example, the logic module 589 of fig. 5 receives an indication of a reference power and mode. In this example, the logic module 589 generates a power threshold based on the reference power and the mode. The series module 104 modifies the resistance of the series module 104 based on the power threshold to limit the amount of power at the LEDs 120 (812). For example, the error amplifier 382 of the series module 304 of fig. 3 may cause the switching element 384 to modify the resistance of the series module 304 to limit the amount of power at the LED 320. In another example, the error amplifier 482 of the control module 408 of fig. 4 may cause the switching element 484 to modify the resistance of the series module 404 to limit the amount of power at the LED 420.

The following examples may illustrate one or more aspects of the present disclosure.

Example 1. a system, comprising: a power module configured to generate supply power; a loading module configured to select a subset of Light Emitting Diodes (LEDs) from a set of LEDs; a series of modules configured to receive the supply power from the power module, dissipate a portion of the supply power, and output a remaining portion of the supply power as load power to a subset of the LEDs; and a control module configured to drive the series of modules to limit an amount of power at a subset of the LEDs.

The system of example 1, wherein the control module is further configured to generate a target power based on a portion of the supply power dissipated at the series of modules; and to generate the supply power, the power module is configured to generate the supply power based on the target power.

Example 3. the system of any of examples 1-2, wherein the series of modules is configured to dissipate a portion of the supply power such that the load power is less than a maximum power threshold.

Example 4. the system of any of examples 1-3, wherein to drive the series of modules, the control module is configured to output an indication of the maximum power threshold to the series of modules; and to dissipate a portion of the supply power such that the load power is less than a maximum power threshold, the series of modules is configured to modify the resistance of the series of modules based on the indication of the maximum power threshold such that the load power is less than the maximum power threshold.

Example 5. the system of any of examples 1 to 4, wherein the series of modules is configured to dissipate a portion of the supply power such that the load power corresponds to a target power.

Example 6. the system of any of examples 1 to 5, wherein to drive the series of modules, the control module is configured to output an indication of the target power to the series of modules; and to dissipate a portion of the supply power such that the load power corresponds to a target power, the series of modules is configured to modify the resistance of the series of modules based on the indication of the target power such that the load power corresponds to the target power.

Example 7. the system of any of examples 1 to 6, wherein the series of modules is further configured to decouple the power module from the set of LEDs when the loading module selects the subset of LEDs from the set of LEDs.

Example 8 a method comprises: generating supply power by a power module of the circuit; selecting, by a loading module of the circuit, a subset of Light Emitting Diodes (LEDs) from a set of LEDs; receiving, by a series of modules of the circuit, the supply power from the power module; dissipating a portion of the supply power by the series of modules; outputting, by the series of modules, a remaining portion of the supply power as load power to a subset of the LEDs; and driving, by a control module of the circuit, the series of modules to limit an amount of power at a subset of the LEDs.

Example 9. the method of example 8, further comprising: generating, by the control module, a target power based on a portion of the supply power dissipated at the series of modules; and generating the supply power based on the target power.

Example 10. the method of any of examples 8 to 9, wherein dissipating a portion of the supply power comprises: dissipating a portion of the supply power by the series of modules such that the load power is less than a maximum power threshold.

Example 11. the method of any of examples 8 to 10, wherein driving the series of modules comprises: outputting, by the control module to the series module, an indication of the maximum power threshold; and dissipating a portion of the supply power such that the load power is less than the maximum power threshold comprises: modifying, by the series of modules, a resistance of the series of modules based on the indication of the maximum power threshold such that the load power is less than the maximum power threshold.

Example 12. the method of any of examples 8 to 11, wherein dissipating a portion of the supply power comprises: dissipating a portion of the supply power by the series of modules such that the load power corresponds to a target power.

Example 13. the method of any of examples 8 to 12, wherein driving the series of modules comprises: outputting, by the control module to the series module, an indication of the target power; and dissipating a portion of the supply power such that the load power corresponds to the target power comprises: modifying, by the series module, a resistance of the series module based on the indication of the target power such that an amount of power output at the subset of LEDs corresponds to the target power.

Example 14. the method of any of examples 8 to 13, further comprising: decoupling, by the series of modules, the power module from the set of LEDs when the loading module selects the subset of LEDs from the set of LEDs.

Example 15. a system, comprising: a switching logic module configured to generate a switching signal; a set of Light Emitting Diodes (LEDs); a loading module configured to selectively bypass each LED of the set of LEDs to form a subset of LEDs based on the switching signal; a power module configured to output supply power; a series of modules configured to receive the supply power from the power module, dissipate a portion of the supply power, and output a remaining portion of the supply power as load power to a subset of the LEDs; and a control module configured to drive the series of modules to limit an amount of power at a subset of the LEDs.

Example 16. the system of example 15, wherein: the control module is further configured to generate a target power based on a portion of the supply power dissipated at the series of modules; and to generate the supply power, the power module is configured to generate the supply power based on the target power.

The system of any of examples 15-16, wherein to dissipate a portion of the supply power, the series of modules is configured to: receiving an indication of the load power; receiving an indication of a power threshold; and modifying the resistance of the series of modules based on the indication of the load power and the indication of the power threshold.

The system of any of examples 15 to 17, wherein the control module is configured to: receiving an indication of the load power; receiving an indication of a power threshold; and generating a control signal based on the indication of the load power and the indication of the power threshold; and to dissipate a portion of the supply power, the series of modules is configured to modify a resistance of the series of modules based on the control signal.

Example 19. the system of any of examples 15 to 18, further comprising: a logic module configured to: receiving an indication of a selection of a mode and an indication of a reference power; generating the power threshold based on an indication of the selection of the mode and an indication of the reference power; and outputting an indication of the power threshold to the control module.

Example 20. the system of any of examples 15 to 19, wherein the series of modules is further configured to decouple the power module from the set of LEDs when the loading module selectively bypasses each LED of the set of LEDs to form the subset of LEDs.

Various aspects have been described in this disclosure. These and other aspects are within the scope of the appended claims.

Claims

1. A system for driving light emitting diodes, comprising:

a power module configured to generate supply power;

a loading module configured to select a subset of light emitting diodes from a set of light emitting diodes, LEDs;

a series of modules configured to receive the supply power from the power module, dissipate a portion of the supply power, and output a remaining portion of the supply power as load power to a subset of the LEDs; and

a control module configured to drive the series of modules to limit an amount of power at a subset of the LEDs,

wherein, to drive the series of modules, the control module is configured to output an indication of a power threshold or a control signal to the series of modules, an

Wherein, to dissipate a portion of the supply power, the series of modules is configured to modify a resistance of a switching element of the series of modules based on an indication of the power threshold or control signal such that the resistance of the switching element dissipates a portion of the supply power and outputs a remaining portion of the supply power directly to a subset of the LEDs as the load power, wherein the load power output directly to the subset of LEDs by the resistance of the switching element activates the subset of LEDs such that the subset of LEDs emits light using the load power output directly by the resistance of the switching element.

2. The system of claim 1, wherein,

the control module is further configured to generate a target power based on a portion of the supply power dissipated at the series of modules; and

to generate the supply power, the power module is configured to generate the supply power based on the target power.

3. The system of claim 1, wherein the power threshold or control signal is a maximum power threshold, and wherein to dissipate a portion of the supply power, the series of modules are configured to dissipate a portion of the supply power such that the load power is less than the maximum power threshold.

4. The system of claim 3, wherein,

to modify the resistance of the series of modules, the series of modules is configured to modify the resistance of the series of modules based on the indication of the maximum power threshold such that the load power is less than the maximum power threshold.

5. The system of claim 1, wherein the power threshold or control signal corresponds to a target power, and wherein the series of modules is configured to dissipate a portion of the supply power such that the load power corresponds to the target power.

6. The system of claim 5, wherein,

to modify the resistance of the series of modules, the series of modules is configured to modify the resistance of the series of modules based on the indication of the target power such that the load power corresponds to the target power.

7. The system of claim 1, wherein the series of modules is further configured to: decoupling the power module from the set of LEDs when the loading module selects the subset of LEDs from the set of LEDs.

8. The system of claim 1, wherein to modify the resistance of the switching elements of the series of modules, the series of modules is configured to increase the resistance of the switching elements to increase a portion of the supply power dissipated by the resistance of the switching elements.

9. A method of driving a light emitting diode, comprising:

generating supply power by a power module of the circuit;

selecting, by a loading module of the circuit, a subset of light emitting diodes from a set of light emitting diodes, LEDs;

receiving, by a series of modules of the circuit, the supply power from the power module;

dissipating a portion of the supply power by the series of modules;

outputting, by the series of modules, a remaining portion of the supply power as load power to a subset of the LEDs; and

driving the series of modules by a control module of the circuit to limit an amount of power at a subset of the LEDs,

wherein driving the series of modules comprises outputting an indication of a power threshold or a control signal to the series of modules, an

Wherein dissipating a portion of the supply power comprises modifying a resistance of a switching element of the series of modules based on an indication of the power threshold or control signal such that the resistance of the switching element dissipates a portion of the supply power and outputs a remaining portion of the supply power directly to a subset of the LEDs as the load power, wherein the load power output directly to the subset of LEDs by the resistance of the switching element activates the subset of LEDs such that the subset of LEDs emits light using the load power output directly by the resistance of the switching element.

10. The method of claim 9, further comprising: generating, by the control module, a target power based on a portion of the supply power dissipated at the series of modules, wherein the supply power is generated based on the target power.

11. The method of claim 9, wherein the power threshold or control signal is a maximum power threshold, and wherein dissipating a portion of the supply power comprises: dissipating a portion of the supply power by the series of modules such that the load power is less than the maximum power threshold.

12. The method of claim 11, wherein,

modifying the resistance of the series of modules includes: modifying, by the series of modules, a resistance of the series of modules based on the indication of the maximum power threshold such that the load power is less than the maximum power threshold.

13. The method of claim 9, wherein the power threshold or control signal corresponds to a target power, and wherein dissipating a portion of the supply power comprises: dissipating a portion of the supply power by the series of modules such that the load power corresponds to the target power.

14. The method of claim 13, wherein,

modifying the resistance of the series of modules includes: modifying, by the series module, a resistance of the series module based on the indication of the target power such that an amount of power output at the subset of LEDs corresponds to the target power.

15. The method of claim 9, further comprising:

decoupling, by the series of modules, the power module from the set of LEDs when the loading module selects the subset of LEDs from the set of LEDs.

16. A system for preventing current overshoot, comprising:

a switching logic module configured to generate a switching signal;

a set of light emitting diodes, LEDs;

a loading module configured to selectively bypass each LED of the set of LEDs to form a subset of LEDs based on the switching signal;

a power module configured to output supply power;

17. The system of claim 16, wherein,

18. The system of claim 16, wherein to drive the series of modules, the control module is configured to output an indication of the power threshold to the series of modules, and wherein to dissipate a portion of the supply power, the series of modules is configured to:

receiving an indication of the load power;

receiving an indication of the power threshold; and

the resistance of the series of modules is also modified based on the indication of the load power.

19. The system of claim 16, wherein, to drive the series of modules, the control module is configured to output an indication of the control signal to the series of modules, and wherein,

the control module is configured to:

receiving an indication of the load power;

receiving an indication of the power threshold; and

generating the control signal based on the indication of the load power and the power threshold; and

to dissipate a portion of the supply power, the series of modules is configured to modify a resistance of the series of modules based on the control signal.

20. The system of claim 19, further comprising: a logic module configured to:

receiving an indication of a selection of a mode and an indication of a reference power;

generating the power threshold based on an indication of the selection of the mode and an indication of the reference power; and

outputting an indication of the power threshold to the control module.

21. The system of claim 16, wherein the series of modules is further configured to decouple the power module from the set of LEDs when the load module selectively bypasses each LED in the set of LEDs to form the subset of LEDs.